Summary:
Geology at Ming Mine
Geology within the Property area has been resolved as two major lithological packages, the Hanging Wall Sequence, and the underlying Mineralized Sequence. The contact between the two is a metre scale zone of significant brittle-ductile shearing which is parallel to the strong C-S fabric in the rocks below. The Hanging Wall Sequence consists mainly of basaltic flows with lesser volcaniclastic and volcanogenic sediments, including minor magnetic iron formation. The underlying Mineralized Sequence consists dominantly of altered and locally mineralized, quartz-phyric felsic volcanic rocks with minor quantities of altered basalt. Local structural fabrics are developed more strongly in the altered rocks of the Mineralized Sequence. Both the Hanging Wall and Mineralized Sequences are cut by significant volumes of gabbroic sills and dykes.
Banded, pyritic massive sulphides on the Ming Massive Sulphide Horizon (MMS) occur directly below the sheared contact separating the Hanging Wall and Mineralized Sequences. More than one horizon of massive sulphide has been intersected in several holes; in these instances, the massive sulphide zones are separated by altered, pyritized felsic volcanic or by gabbroic intrusive rocks. Immediately below the MMS occurs a sericitized-pyritized felsic unit approximately 15 to 20 m thick. This unit is characterized by the variable presence of green mica and higher than normal gold concentrations. Gold concentrations diminish while moving deeper in the stratigraphy and away from the MMS horizon. Below this gold-enriched horizon lies a sequence of sericitized-pyritized felsic volcanics 100 m in thickness which separates the mineralization on the MMS horizon from that in the Lower Footwall Zone (LFZ).
The LFZ consists of nebulous zones of disseminated and stringer chalcopyrite-pyrrhotite cutting altered felsic and lesser mafic volcanic rocks. Alteration is dominantly sericitic in less mineralized areas of the zone and distinctly chloritic in areas that contain higher copper concentrations. The gold to copper ratio in the MMS is approximately 1:2.
Mineralization
The polymetallic sulphide deposits in the Ming Mine area are known to contain copper, zinc and minor lead, gold and silver along with traces of other metals. Mineralization in the deposits has been classified in the past as either massive sulphide, footwall stringer, or disseminated ore.
Exploration on the Ming deposit has identified distinct zones of sulphide mineralization. This, in conjunction with ongoing academic studies, imply a somewhat greater complexity in orogeny of the Ming Mine and other deposits in the area based on distinct alteration and sulphide assemblages, mineralogical and textural variations and the structural setting of mineralization. For the current documentation there remain two dominant types of mineralization in the Ming deposit:
-Stratiform volcanogenic massive sulphide (MMS); and
-Disseminated stringers of sulphides (LFZ).
The MMS is recognized as a series of horizons which are open at depth, thickness ranges between 2 m and 5 m, locally up to 10 m with a strike length of at least 100 m. Like other deposits in the area, it follows D2 planar fabric and is roughly parallel to the D2 extension lineation plunging 30 to 35 degrees northeast to a vertical depth of at least 1,200 m. Several textural varieties of mineralization are recognized in the MMS horizon including massive pyrite ore, banded ore, massive chalcopyrite-pyrrhotite ore, and breccia ore.
The MMS has three different ore types: i) massive pyrite ore, which is less than 70% pyrite, with chalcopyrite and minor amounts of galena, sphalerite, and silicate minerals, ii) banded ore consists of alternating bands of pyrite and chalcopyrite-quartz-actinolite-biotite and iii) Massive chalcopyrite-pyrrhotite ore occurs as lenses and layers with up to 80% chalcopyrite. Minor amounts of arsenopyrite, galena, tetrahedrite, native gold, tennantite, and cubanite occur locally. There is up to 10% disseminated pyrite in the immediate footwall.
The LFZ is another mineralized horizon that lies approximately 100 m below the MMS horizon. The LFZ strike length is approximately 1,700 m and has a thickness that varies from 200 m to 290 m. Base metal assays from drilling are variable indicating that there are clusters of chalcopyrite and pyrite / pyrrhotite stringers which are separated by less mineralized rock. Gold values in the LFZ are generally less than 0.5 g/t and only trace amounts of zinc have been reported. The LFZ is transected by fine to medium grained basic dykes interpreted as feeder dykes to a mafic sequence in the hanging wall above the MMS.
The LFZ is an alteration zone consisting dominantly of chloritic schist that contains varying percentages of chalcopyrite and pyrite which occur as stringers with lesser amounts of pyrrhotite and sphalerite. The LFZ is parallel to the D2 planar fabric and extension lineation, appears to be conformable to the overlying MMS and as such, can be interpreted as the feeder or stockwork alteration zone to the MMS a relationship consistent with the VMS model. The exact location of the hydrothermal conduit responsible for alteration in the LFZ and mineralization in the overlying MMS has been obscured through deformation; however, in its plunge direction, the LFZ itself may represent a structural conduit that allowed the ascent of hydrothermal fluid. The extent of the LFZ is unknown as it is open both up and down plunge.
Deposit Types
The Property is a Noranda-type VMS deposit hosted by Cambrian-Ordovician metavolcanic and metasedimentary rocks of the Pacquet Harbour Group. The style of mineralization, alteration, host rock, and tectonism most closely resembles other VMS deposits throughout the world.
This deposit type is characterized by the following geologic elements.
-Geological setting:
-Island arc;
-Typically in a local extensional setting or rift environment within, or perhaps behind, an oceanic or continental margin arc Marine volcanism;
-Commonly during a period of more felsic volcanism in an andesite (or basalt) dominated succession;
-Locally associated with fine-grained marine sediments;
-Also associated with faults or prominent fractures.
Host rock types:
-Submarine volcanic arc rocks: rhyolite, dacite associated with andesite or basalt;
-Less commonly, in mafic alkaline arc successions;
-Associated epiclastic deposits and minor shale or sandstone;
-Commonly in close proximity to felsic intrusive rocks;
-Ore horizon grades laterally and vertically into thin chert or sediment layers called informally exhalites.
Deposit forms:
-Concordant massive to banded sulphide lens which is typically metres to tens of metres thick and tens to hundreds of metres in horizontal dimension;
-Sometimes there is a peripheral apron of "clastic" massive sulphides.
Ore mineralogy:
-Upper massive zone: pyrite, sphalerite, galena, chalcopyrite, pyrrhotite, tetrahedrite, tennantite, bornite, arsenopyrite;
-Lower massive zone: pyrite, chalcopyrite, sphalerite, pyrrhotite, magnetite.
Alteration:
-Footwall alteration pipes are commonly zoned from the core with quartz, sericite or chlorite to an outer zone of clay minerals, albite and carbonate (siderite or ankerite).